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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.util;

import java.io.*;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.DoubleConsumer;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.StreamSupport;

import sun.misc.Unsafe;

/**
 * An instance of this class is used to generate a stream of
 * pseudorandom numbers. The class uses a 48-bit seed, which is
 * modified using a linear congruential formula. (See Donald Knuth,
 * <i>The Art of Computer Programming, Volume 2</i>, Section 3.2.1.)
 * <p>
 * If two instances of {@code Random} are created with the same
 * seed, and the same sequence of method calls is made for each, they
 * will generate and return identical sequences of numbers. In order to
 * guarantee this property, particular algorithms are specified for the
 * class {@code Random}. Java implementations must use all the algorithms
 * shown here for the class {@code Random}, for the sake of absolute
 * portability of Java code. However, subclasses of class {@code Random}
 * are permitted to use other algorithms, so long as they adhere to the
 * general contracts for all the methods.
 * <p>
 * The algorithms implemented by class {@code Random} use a
 * {@code protected} utility method that on each invocation can supply
 * up to 32 pseudorandomly generated bits.
 * <p>
 * Many applications will find the method {@link Math#random} simpler to use.
 *
 * <p>Instances of {@code java.util.Random} are threadsafe.
 * However, the concurrent use of the same {@code java.util.Random}
 * instance across threads may encounter contention and consequent
 * poor performance. Consider instead using
 * {@link java.util.concurrent.ThreadLocalRandom} in multithreaded
 * designs.
 *
 * <p>Instances of {@code java.util.Random} are not cryptographically
 * secure.  Consider instead using {@link java.security.SecureRandom} to
 * get a cryptographically secure pseudo-random number generator for use
 * by security-sensitive applications.
 *
 * @author Frank Yellin
 * @since 1.0
 */
public class Random implements java.io.Serializable {

  /**
   * use serialVersionUID from JDK 1.1 for interoperability
   */
  static final long serialVersionUID = 3905348978240129619L;

  /**
   * The internal state associated with this pseudorandom number generator.
   * (The specs for the methods in this class describe the ongoing
   * computation of this value.)
   */
  private final AtomicLong seed;

  private static final long multiplier = 0x5DEECE66DL;
  private static final long addend = 0xBL;
  private static final long mask = (1L << 48) - 1;

  private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)

  // IllegalArgumentException messages
  static final String BadBound = "bound must be positive";
  static final String BadRange = "bound must be greater than origin";
  static final String BadSize = "size must be non-negative";

  /**
   * Creates a new random number generator. This constructor sets
   * the seed of the random number generator to a value very likely
   * to be distinct from any other invocation of this constructor.
   */
  public Random() {
    this(seedUniquifier() ^ System.nanoTime());
  }

  private static long seedUniquifier() {
    // L'Ecuyer, "Tables of Linear Congruential Generators of
    // Different Sizes and Good Lattice Structure", 1999
    for (; ; ) {
      long current = seedUniquifier.get();
      long next = current * 181783497276652981L;
      if (seedUniquifier.compareAndSet(current, next)) {
        return next;
      }
    }
  }

  private static final AtomicLong seedUniquifier
      = new AtomicLong(8682522807148012L);

  /**
   * Creates a new random number generator using a single {@code long} seed.
   * The seed is the initial value of the internal state of the pseudorandom
   * number generator which is maintained by method {@link #next}.
   *
   * <p>The invocation {@code new Random(seed)} is equivalent to:
   * <pre> {@code
   * Random rnd = new Random();
   * rnd.setSeed(seed);}</pre>
   *
   * @param seed the initial seed
   * @see #setSeed(long)
   */
  public Random(long seed) {
    if (getClass() == Random.class) {
      this.seed = new AtomicLong(initialScramble(seed));
    } else {
      // subclass might have overriden setSeed
      this.seed = new AtomicLong();
      setSeed(seed);
    }
  }

  private static long initialScramble(long seed) {
    return (seed ^ multiplier) & mask;
  }

  /**
   * Sets the seed of this random number generator using a single
   * {@code long} seed. The general contract of {@code setSeed} is
   * that it alters the state of this random number generator object
   * so as to be in exactly the same state as if it had just been
   * created with the argument {@code seed} as a seed. The method
   * {@code setSeed} is implemented by class {@code Random} by
   * atomically updating the seed to
   * <pre>{@code (seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)}</pre>
   * and clearing the {@code haveNextNextGaussian} flag used by {@link
   * #nextGaussian}.
   *
   * <p>The implementation of {@code setSeed} by class {@code Random}
   * happens to use only 48 bits of the given seed. In general, however,
   * an overriding method may use all 64 bits of the {@code long}
   * argument as a seed value.
   *
   * @param seed the initial seed
   */
  synchronized public void setSeed(long seed) {
    this.seed.set(initialScramble(seed));
    haveNextNextGaussian = false;
  }

  /**
   * Generates the next pseudorandom number. Subclasses should
   * override this, as this is used by all other methods.
   *
   * <p>The general contract of {@code next} is that it returns an
   * {@code int} value and if the argument {@code bits} is between
   * {@code 1} and {@code 32} (inclusive), then that many low-order
   * bits of the returned value will be (approximately) independently
   * chosen bit values, each of which is (approximately) equally
   * likely to be {@code 0} or {@code 1}. The method {@code next} is
   * implemented by class {@code Random} by atomically updating the seed to
   * <pre>{@code (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)}</pre>
   * and returning
   * <pre>{@code (int)(seed >>> (48 - bits))}.</pre>
   *
   * This is a linear congruential pseudorandom number generator, as
   * defined by D. H. Lehmer and described by Donald E. Knuth in
   * <i>The Art of Computer Programming,</i> Volume 3:
   * <i>Seminumerical Algorithms</i>, section 3.2.1.
   *
   * @param bits random bits
   * @return the next pseudorandom value from this random number generator's sequence
   * @since 1.1
   */
  protected int next(int bits) {
    long oldseed, nextseed;
    AtomicLong seed = this.seed;
    do {
      oldseed = seed.get();
      nextseed = (oldseed * multiplier + addend) & mask;
    } while (!seed.compareAndSet(oldseed, nextseed));
    return (int) (nextseed >>> (48 - bits));
  }

  /**
   * Generates random bytes and places them into a user-supplied
   * byte array.  The number of random bytes produced is equal to
   * the length of the byte array.
   *
   * <p>The method {@code nextBytes} is implemented by class {@code Random}
   * as if by:
   * <pre> {@code
   * public void nextBytes(byte[] bytes) {
   *   for (int i = 0; i < bytes.length; )
   *     for (int rnd = nextInt(), n = Math.min(bytes.length - i, 4);
   *          n-- > 0; rnd >>= 8)
   *       bytes[i++] = (byte)rnd;
   * }}</pre>
   *
   * @param bytes the byte array to fill with random bytes
   * @throws NullPointerException if the byte array is null
   * @since 1.1
   */
  public void nextBytes(byte[] bytes) {
    for (int i = 0, len = bytes.length; i < len; ) {
      for (int rnd = nextInt(),
          n = Math.min(len - i, Integer.SIZE / Byte.SIZE);
          n-- > 0; rnd >>= Byte.SIZE) {
        bytes[i++] = (byte) rnd;
      }
    }
  }

  /**
   * The form of nextLong used by LongStream Spliterators.  If
   * origin is greater than bound, acts as unbounded form of
   * nextLong, else as bounded form.
   *
   * @param origin the least value, unless greater than bound
   * @param bound the upper bound (exclusive), must not equal origin
   * @return a pseudorandom value
   */
  final long internalNextLong(long origin, long bound) {
    long r = nextLong();
    if (origin < bound) {
      long n = bound - origin, m = n - 1;
      if ((n & m) == 0L)  // power of two
      {
        r = (r & m) + origin;
      } else if (n > 0L) {  // reject over-represented candidates
        for (long u = r >>> 1;            // ensure nonnegative
            u + m - (r = u % n) < 0L;    // rejection check
            u = nextLong() >>> 1) // retry
        {
          ;
        }
        r += origin;
      } else {              // range not representable as long
        while (r < origin || r >= bound) {
          r = nextLong();
        }
      }
    }
    return r;
  }

  /**
   * The form of nextInt used by IntStream Spliterators.
   * For the unbounded case: uses nextInt().
   * For the bounded case with representable range: uses nextInt(int bound)
   * For the bounded case with unrepresentable range: uses nextInt()
   *
   * @param origin the least value, unless greater than bound
   * @param bound the upper bound (exclusive), must not equal origin
   * @return a pseudorandom value
   */
  final int internalNextInt(int origin, int bound) {
    if (origin < bound) {
      int n = bound - origin;
      if (n > 0) {
        return nextInt(n) + origin;
      } else {  // range not representable as int
        int r;
        do {
          r = nextInt();
        } while (r < origin || r >= bound);
        return r;
      }
    } else {
      return nextInt();
    }
  }

  /**
   * The form of nextDouble used by DoubleStream Spliterators.
   *
   * @param origin the least value, unless greater than bound
   * @param bound the upper bound (exclusive), must not equal origin
   * @return a pseudorandom value
   */
  final double internalNextDouble(double origin, double bound) {
    double r = nextDouble();
    if (origin < bound) {
      r = r * (bound - origin) + origin;
      if (r >= bound) // correct for rounding
      {
        r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
      }
    }
    return r;
  }

  /**
   * Returns the next pseudorandom, uniformly distributed {@code int}
   * value from this random number generator's sequence. The general
   * contract of {@code nextInt} is that one {@code int} value is
   * pseudorandomly generated and returned. All 2<sup>32</sup> possible
   * {@code int} values are produced with (approximately) equal probability.
   *
   * <p>The method {@code nextInt} is implemented by class {@code Random}
   * as if by:
   * <pre> {@code
   * public int nextInt() {
   *   return next(32);
   * }}</pre>
   *
   * @return the next pseudorandom, uniformly distributed {@code int} value from this random number
   * generator's sequence
   */
  public int nextInt() {
    return next(32);
  }

  /**
   * Returns a pseudorandom, uniformly distributed {@code int} value
   * between 0 (inclusive) and the specified value (exclusive), drawn from
   * this random number generator's sequence.  The general contract of
   * {@code nextInt} is that one {@code int} value in the specified range
   * is pseudorandomly generated and returned.  All {@code bound} possible
   * {@code int} values are produced with (approximately) equal
   * probability.  The method {@code nextInt(int bound)} is implemented by
   * class {@code Random} as if by:
   * <pre> {@code
   * public int nextInt(int bound) {
   *   if (bound <= 0)
   *     throw new IllegalArgumentException("bound must be positive");
   *
   *   if ((bound & -bound) == bound)  // i.e., bound is a power of 2
   *     return (int)((bound * (long)next(31)) >> 31);
   *
   *   int bits, val;
   *   do {
   *       bits = next(31);
   *       val = bits % bound;
   *   } while (bits - val + (bound-1) < 0);
   *   return val;
   * }}</pre>
   *
   * <p>The hedge "approximately" is used in the foregoing description only
   * because the next method is only approximately an unbiased source of
   * independently chosen bits.  If it were a perfect source of randomly
   * chosen bits, then the algorithm shown would choose {@code int}
   * values from the stated range with perfect uniformity.
   * <p>
   * The algorithm is slightly tricky.  It rejects values that would result
   * in an uneven distribution (due to the fact that 2^31 is not divisible
   * by n). The probability of a value being rejected depends on n.  The
   * worst case is n=2^30+1, for which the probability of a reject is 1/2,
   * and the expected number of iterations before the loop terminates is 2.
   * <p>
   * The algorithm treats the case where n is a power of two specially: it
   * returns the correct number of high-order bits from the underlying
   * pseudo-random number generator.  In the absence of special treatment,
   * the correct number of <i>low-order</i> bits would be returned.  Linear
   * congruential pseudo-random number generators such as the one
   * implemented by this class are known to have short periods in the
   * sequence of values of their low-order bits.  Thus, this special case
   * greatly increases the length of the sequence of values returned by
   * successive calls to this method if n is a small power of two.
   *
   * @param bound the upper bound (exclusive).  Must be positive.
   * @return the next pseudorandom, uniformly distributed {@code int} value between zero (inclusive)
   * and {@code bound} (exclusive) from this random number generator's sequence
   * @throws IllegalArgumentException if bound is not positive
   * @since 1.2
   */
  public int nextInt(int bound) {
    if (bound <= 0) {
      throw new IllegalArgumentException(BadBound);
    }

    int r = next(31);
    int m = bound - 1;
    if ((bound & m) == 0)  // i.e., bound is a power of 2
    {
      r = (int) ((bound * (long) r) >> 31);
    } else {
      for (int u = r;
          u - (r = u % bound) + m < 0;
          u = next(31)) {
        ;
      }
    }
    return r;
  }

  /**
   * Returns the next pseudorandom, uniformly distributed {@code long}
   * value from this random number generator's sequence. The general
   * contract of {@code nextLong} is that one {@code long} value is
   * pseudorandomly generated and returned.
   *
   * <p>The method {@code nextLong} is implemented by class {@code Random}
   * as if by:
   * <pre> {@code
   * public long nextLong() {
   *   return ((long)next(32) << 32) + next(32);
   * }}</pre>
   *
   * Because class {@code Random} uses a seed with only 48 bits,
   * this algorithm will not return all possible {@code long} values.
   *
   * @return the next pseudorandom, uniformly distributed {@code long} value from this random number
   * generator's sequence
   */
  public long nextLong() {
    // it's okay that the bottom word remains signed.
    return ((long) (next(32)) << 32) + next(32);
  }

  /**
   * Returns the next pseudorandom, uniformly distributed
   * {@code boolean} value from this random number generator's
   * sequence. The general contract of {@code nextBoolean} is that one
   * {@code boolean} value is pseudorandomly generated and returned.  The
   * values {@code true} and {@code false} are produced with
   * (approximately) equal probability.
   *
   * <p>The method {@code nextBoolean} is implemented by class {@code Random}
   * as if by:
   * <pre> {@code
   * public boolean nextBoolean() {
   *   return next(1) != 0;
   * }}</pre>
   *
   * @return the next pseudorandom, uniformly distributed {@code boolean} value from this random
   * number generator's sequence
   * @since 1.2
   */
  public boolean nextBoolean() {
    return next(1) != 0;
  }

  /**
   * Returns the next pseudorandom, uniformly distributed {@code float}
   * value between {@code 0.0} and {@code 1.0} from this random
   * number generator's sequence.
   *
   * <p>The general contract of {@code nextFloat} is that one
   * {@code float} value, chosen (approximately) uniformly from the
   * range {@code 0.0f} (inclusive) to {@code 1.0f} (exclusive), is
   * pseudorandomly generated and returned. All 2<sup>24</sup> possible
   * {@code float} values of the form <i>m&nbsp;x&nbsp;</i>2<sup>-24</sup>,
   * where <i>m</i> is a positive integer less than 2<sup>24</sup>, are
   * produced with (approximately) equal probability.
   *
   * <p>The method {@code nextFloat} is implemented by class {@code Random}
   * as if by:
   * <pre> {@code
   * public float nextFloat() {
   *   return next(24) / ((float)(1 << 24));
   * }}</pre>
   *
   * <p>The hedge "approximately" is used in the foregoing description only
   * because the next method is only approximately an unbiased source of
   * independently chosen bits. If it were a perfect source of randomly
   * chosen bits, then the algorithm shown would choose {@code float}
   * values from the stated range with perfect uniformity.<p>
   * [In early versions of Java, the result was incorrectly calculated as:
   * <pre> {@code
   *   return next(30) / ((float)(1 << 30));}</pre>
   * This might seem to be equivalent, if not better, but in fact it
   * introduced a slight nonuniformity because of the bias in the rounding
   * of floating-point numbers: it was slightly more likely that the
   * low-order bit of the significand would be 0 than that it would be 1.]
   *
   * @return the next pseudorandom, uniformly distributed {@code float} value between {@code 0.0}
   * and {@code 1.0} from this random number generator's sequence
   */
  public float nextFloat() {
    return next(24) / ((float) (1 << 24));
  }

  /**
   * Returns the next pseudorandom, uniformly distributed
   * {@code double} value between {@code 0.0} and
   * {@code 1.0} from this random number generator's sequence.
   *
   * <p>The general contract of {@code nextDouble} is that one
   * {@code double} value, chosen (approximately) uniformly from the
   * range {@code 0.0d} (inclusive) to {@code 1.0d} (exclusive), is
   * pseudorandomly generated and returned.
   *
   * <p>The method {@code nextDouble} is implemented by class {@code Random}
   * as if by:
   * <pre> {@code
   * public double nextDouble() {
   *   return (((long)next(26) << 27) + next(27))
   *     / (double)(1L << 53);
   * }}</pre>
   *
   * <p>The hedge "approximately" is used in the foregoing description only
   * because the {@code next} method is only approximately an unbiased
   * source of independently chosen bits. If it were a perfect source of
   * randomly chosen bits, then the algorithm shown would choose
   * {@code double} values from the stated range with perfect uniformity.
   * <p>[In early versions of Java, the result was incorrectly calculated as:
   * <pre> {@code
   *   return (((long)next(27) << 27) + next(27))
   *     / (double)(1L << 54);}</pre>
   * This might seem to be equivalent, if not better, but in fact it
   * introduced a large nonuniformity because of the bias in the rounding
   * of floating-point numbers: it was three times as likely that the
   * low-order bit of the significand would be 0 than that it would be 1!
   * This nonuniformity probably doesn't matter much in practice, but we
   * strive for perfection.]
   *
   * @return the next pseudorandom, uniformly distributed {@code double} value between {@code 0.0}
   * and {@code 1.0} from this random number generator's sequence
   * @see Math#random
   */
  public double nextDouble() {
    return (((long) (next(26)) << 27) + next(27)) * DOUBLE_UNIT;
  }

  private double nextNextGaussian;
  private boolean haveNextNextGaussian = false;

  /**
   * Returns the next pseudorandom, Gaussian ("normally") distributed
   * {@code double} value with mean {@code 0.0} and standard
   * deviation {@code 1.0} from this random number generator's sequence.
   * <p>
   * The general contract of {@code nextGaussian} is that one
   * {@code double} value, chosen from (approximately) the usual
   * normal distribution with mean {@code 0.0} and standard deviation
   * {@code 1.0}, is pseudorandomly generated and returned.
   *
   * <p>The method {@code nextGaussian} is implemented by class
   * {@code Random} as if by a threadsafe version of the following:
   * <pre> {@code
   * private double nextNextGaussian;
   * private boolean haveNextNextGaussian = false;
   *
   * public double nextGaussian() {
   *   if (haveNextNextGaussian) {
   *     haveNextNextGaussian = false;
   *     return nextNextGaussian;
   *   } else {
   *     double v1, v2, s;
   *     do {
   *       v1 = 2 * nextDouble() - 1;   // between -1.0 and 1.0
   *       v2 = 2 * nextDouble() - 1;   // between -1.0 and 1.0
   *       s = v1 * v1 + v2 * v2;
   *     } while (s >= 1 || s == 0);
   *     double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
   *     nextNextGaussian = v2 * multiplier;
   *     haveNextNextGaussian = true;
   *     return v1 * multiplier;
   *   }
   * }}</pre>
   * This uses the <i>polar method</i> of G. E. P. Box, M. E. Muller, and
   * G. Marsaglia, as described by Donald E. Knuth in <i>The Art of
   * Computer Programming</i>, Volume 3: <i>Seminumerical Algorithms</i>,
   * section 3.4.1, subsection C, algorithm P. Note that it generates two
   * independent values at the cost of only one call to {@code StrictMath.log}
   * and one call to {@code StrictMath.sqrt}.
   *
   * @return the next pseudorandom, Gaussian ("normally") distributed {@code double} value with mean
   * {@code 0.0} and standard deviation {@code 1.0} from this random number generator's sequence
   */
  synchronized public double nextGaussian() {
    // See Knuth, ACP, Section 3.4.1 Algorithm C.
    if (haveNextNextGaussian) {
      haveNextNextGaussian = false;
      return nextNextGaussian;
    } else {
      double v1, v2, s;
      do {
        v1 = 2 * nextDouble() - 1; // between -1 and 1
        v2 = 2 * nextDouble() - 1; // between -1 and 1
        s = v1 * v1 + v2 * v2;
      } while (s >= 1 || s == 0);
      double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s) / s);
      nextNextGaussian = v2 * multiplier;
      haveNextNextGaussian = true;
      return v1 * multiplier;
    }
  }

  // stream methods, coded in a way intended to better isolate for
  // maintenance purposes the small differences across forms.

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code int} values.
   *
   * <p>A pseudorandom {@code int} value is generated as if it's the result of
   * calling the method {@link #nextInt()}.
   *
   * @param streamSize the number of values to generate
   * @return a stream of pseudorandom {@code int} values
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   * @since 1.8
   */
  public IntStream ints(long streamSize) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, streamSize, Integer.MAX_VALUE, 0),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code int}
   * values.
   *
   * <p>A pseudorandom {@code int} value is generated as if it's the result of
   * calling the method {@link #nextInt()}.
   *
   * @return a stream of pseudorandom {@code int} values
   * @implNote This method is implemented to be equivalent to {@code ints(Long.MAX_VALUE)}.
   * @since 1.8
   */
  public IntStream ints() {
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number
   * of pseudorandom {@code int} values, each conforming to the given
   * origin (inclusive) and bound (exclusive).
   *
   * <p>A pseudorandom {@code int} value is generated as if it's the result of
   * calling the following method with the origin and bound:
   * <pre> {@code
   * int nextInt(int origin, int bound) {
   *   int n = bound - origin;
   *   if (n > 0) {
   *     return nextInt(n) + origin;
   *   }
   *   else {  // range not representable as int
   *     int r;
   *     do {
   *       r = nextInt();
   *     } while (r < origin || r >= bound);
   *     return r;
   *   }
   * }}</pre>
   *
   * @param streamSize the number of values to generate
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code int} values, each with the given origin (inclusive) and
   * bound (exclusive)
   * @throws IllegalArgumentException if {@code streamSize} is less than zero, or {@code
   * randomNumberOrigin} is greater than or equal to {@code randomNumberBound}
   * @since 1.8
   */
  public IntStream ints(long streamSize, int randomNumberOrigin,
      int randomNumberBound) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * int} values, each conforming to the given origin (inclusive) and bound
   * (exclusive).
   *
   * <p>A pseudorandom {@code int} value is generated as if it's the result of
   * calling the following method with the origin and bound:
   * <pre> {@code
   * int nextInt(int origin, int bound) {
   *   int n = bound - origin;
   *   if (n > 0) {
   *     return nextInt(n) + origin;
   *   }
   *   else {  // range not representable as int
   *     int r;
   *     do {
   *       r = nextInt();
   *     } while (r < origin || r >= bound);
   *     return r;
   *   }
   * }}</pre>
   *
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code int} values, each with the given origin (inclusive) and
   * bound (exclusive)
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @implNote This method is implemented to be equivalent to {@code ints(Long.MAX_VALUE,
   * randomNumberOrigin, randomNumberBound)}.
   * @since 1.8
   */
  public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code long} values.
   *
   * <p>A pseudorandom {@code long} value is generated as if it's the result
   * of calling the method {@link #nextLong()}.
   *
   * @param streamSize the number of values to generate
   * @return a stream of pseudorandom {@code long} values
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   * @since 1.8
   */
  public LongStream longs(long streamSize) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, streamSize, Long.MAX_VALUE, 0L),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code long}
   * values.
   *
   * <p>A pseudorandom {@code long} value is generated as if it's the result
   * of calling the method {@link #nextLong()}.
   *
   * @return a stream of pseudorandom {@code long} values
   * @implNote This method is implemented to be equivalent to {@code longs(Long.MAX_VALUE)}.
   * @since 1.8
   */
  public LongStream longs() {
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code long}, each conforming to the given origin
   * (inclusive) and bound (exclusive).
   *
   * <p>A pseudorandom {@code long} value is generated as if it's the result
   * of calling the following method with the origin and bound:
   * <pre> {@code
   * long nextLong(long origin, long bound) {
   *   long r = nextLong();
   *   long n = bound - origin, m = n - 1;
   *   if ((n & m) == 0L)  // power of two
   *     r = (r & m) + origin;
   *   else if (n > 0L) {  // reject over-represented candidates
   *     for (long u = r >>> 1;            // ensure nonnegative
   *          u + m - (r = u % n) < 0L;    // rejection check
   *          u = nextLong() >>> 1) // retry
   *         ;
   *     r += origin;
   *   }
   *   else {              // range not representable as long
   *     while (r < origin || r >= bound)
   *       r = nextLong();
   *   }
   *   return r;
   * }}</pre>
   *
   * @param streamSize the number of values to generate
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code long} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code streamSize} is less than zero, or {@code
   * randomNumberOrigin} is greater than or equal to {@code randomNumberBound}
   * @since 1.8
   */
  public LongStream longs(long streamSize, long randomNumberOrigin,
      long randomNumberBound) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * long} values, each conforming to the given origin (inclusive) and bound
   * (exclusive).
   *
   * <p>A pseudorandom {@code long} value is generated as if it's the result
   * of calling the following method with the origin and bound:
   * <pre> {@code
   * long nextLong(long origin, long bound) {
   *   long r = nextLong();
   *   long n = bound - origin, m = n - 1;
   *   if ((n & m) == 0L)  // power of two
   *     r = (r & m) + origin;
   *   else if (n > 0L) {  // reject over-represented candidates
   *     for (long u = r >>> 1;            // ensure nonnegative
   *          u + m - (r = u % n) < 0L;    // rejection check
   *          u = nextLong() >>> 1) // retry
   *         ;
   *     r += origin;
   *   }
   *   else {              // range not representable as long
   *     while (r < origin || r >= bound)
   *       r = nextLong();
   *   }
   *   return r;
   * }}</pre>
   *
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code long} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @implNote This method is implemented to be equivalent to {@code longs(Long.MAX_VALUE,
   * randomNumberOrigin, randomNumberBound)}.
   * @since 1.8
   */
  public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code double} values, each between zero
   * (inclusive) and one (exclusive).
   *
   * <p>A pseudorandom {@code double} value is generated as if it's the result
   * of calling the method {@link #nextDouble()}.
   *
   * @param streamSize the number of values to generate
   * @return a stream of {@code double} values
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   * @since 1.8
   */
  public DoubleStream doubles(long streamSize) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * double} values, each between zero (inclusive) and one
   * (exclusive).
   *
   * <p>A pseudorandom {@code double} value is generated as if it's the result
   * of calling the method {@link #nextDouble()}.
   *
   * @return a stream of pseudorandom {@code double} values
   * @implNote This method is implemented to be equivalent to {@code doubles(Long.MAX_VALUE)}.
   * @since 1.8
   */
  public DoubleStream doubles() {
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code double} values, each conforming to the given origin
   * (inclusive) and bound (exclusive).
   *
   * <p>A pseudorandom {@code double} value is generated as if it's the result
   * of calling the following method with the origin and bound:
   * <pre> {@code
   * double nextDouble(double origin, double bound) {
   *   double r = nextDouble();
   *   r = r * (bound - origin) + origin;
   *   if (r >= bound) // correct for rounding
   *     r = Math.nextDown(bound);
   *   return r;
   * }}</pre>
   *
   * @param streamSize the number of values to generate
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code double} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @since 1.8
   */
  public DoubleStream doubles(long streamSize, double randomNumberOrigin,
      double randomNumberBound) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    if (!(randomNumberOrigin < randomNumberBound)) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * double} values, each conforming to the given origin (inclusive) and bound
   * (exclusive).
   *
   * <p>A pseudorandom {@code double} value is generated as if it's the result
   * of calling the following method with the origin and bound:
   * <pre> {@code
   * double nextDouble(double origin, double bound) {
   *   double r = nextDouble();
   *   r = r * (bound - origin) + origin;
   *   if (r >= bound) // correct for rounding
   *     r = Math.nextDown(bound);
   *   return r;
   * }}</pre>
   *
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code double} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @implNote This method is implemented to be equivalent to {@code doubles(Long.MAX_VALUE,
   * randomNumberOrigin, randomNumberBound)}.
   * @since 1.8
   */
  public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
    if (!(randomNumberOrigin < randomNumberBound)) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Spliterator for int streams.  We multiplex the four int
   * versions into one class by treating a bound less than origin as
   * unbounded, and also by treating "infinite" as equivalent to
   * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
   * approach. The long and double versions of this class are
   * identical except for types.
   */
  static final class RandomIntsSpliterator implements Spliterator.OfInt {

    final Random rng;
    long index;
    final long fence;
    final int origin;
    final int bound;

    RandomIntsSpliterator(Random rng, long index, long fence,
        int origin, int bound) {
      this.rng = rng;
      this.index = index;
      this.fence = fence;
      this.origin = origin;
      this.bound = bound;
    }

    public RandomIntsSpliterator trySplit() {
      long i = index, m = (i + fence) >>> 1;
      return (m <= i) ? null :
          new RandomIntsSpliterator(rng, i, index = m, origin, bound);
    }

    public long estimateSize() {
      return fence - index;
    }

    public int characteristics() {
      return (Spliterator.SIZED | Spliterator.SUBSIZED |
          Spliterator.NONNULL | Spliterator.IMMUTABLE);
    }

    public boolean tryAdvance(IntConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        consumer.accept(rng.internalNextInt(origin, bound));
        index = i + 1;
        return true;
      }
      return false;
    }

    public void forEachRemaining(IntConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        index = f;
        Random r = rng;
        int o = origin, b = bound;
        do {
          consumer.accept(r.internalNextInt(o, b));
        } while (++i < f);
      }
    }
  }

  /**
   * Spliterator for long streams.
   */
  static final class RandomLongsSpliterator implements Spliterator.OfLong {

    final Random rng;
    long index;
    final long fence;
    final long origin;
    final long bound;

    RandomLongsSpliterator(Random rng, long index, long fence,
        long origin, long bound) {
      this.rng = rng;
      this.index = index;
      this.fence = fence;
      this.origin = origin;
      this.bound = bound;
    }

    public RandomLongsSpliterator trySplit() {
      long i = index, m = (i + fence) >>> 1;
      return (m <= i) ? null :
          new RandomLongsSpliterator(rng, i, index = m, origin, bound);
    }

    public long estimateSize() {
      return fence - index;
    }

    public int characteristics() {
      return (Spliterator.SIZED | Spliterator.SUBSIZED |
          Spliterator.NONNULL | Spliterator.IMMUTABLE);
    }

    public boolean tryAdvance(LongConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        consumer.accept(rng.internalNextLong(origin, bound));
        index = i + 1;
        return true;
      }
      return false;
    }

    public void forEachRemaining(LongConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        index = f;
        Random r = rng;
        long o = origin, b = bound;
        do {
          consumer.accept(r.internalNextLong(o, b));
        } while (++i < f);
      }
    }

  }

  /**
   * Spliterator for double streams.
   */
  static final class RandomDoublesSpliterator implements Spliterator.OfDouble {

    final Random rng;
    long index;
    final long fence;
    final double origin;
    final double bound;

    RandomDoublesSpliterator(Random rng, long index, long fence,
        double origin, double bound) {
      this.rng = rng;
      this.index = index;
      this.fence = fence;
      this.origin = origin;
      this.bound = bound;
    }

    public RandomDoublesSpliterator trySplit() {
      long i = index, m = (i + fence) >>> 1;
      return (m <= i) ? null :
          new RandomDoublesSpliterator(rng, i, index = m, origin, bound);
    }

    public long estimateSize() {
      return fence - index;
    }

    public int characteristics() {
      return (Spliterator.SIZED | Spliterator.SUBSIZED |
          Spliterator.NONNULL | Spliterator.IMMUTABLE);
    }

    public boolean tryAdvance(DoubleConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        consumer.accept(rng.internalNextDouble(origin, bound));
        index = i + 1;
        return true;
      }
      return false;
    }

    public void forEachRemaining(DoubleConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        index = f;
        Random r = rng;
        double o = origin, b = bound;
        do {
          consumer.accept(r.internalNextDouble(o, b));
        } while (++i < f);
      }
    }
  }

  /**
   * Serializable fields for Random.
   *
   * @serialField seed long seed for random computations
   * @serialField nextNextGaussian double next Gaussian to be returned
   * @serialField haveNextNextGaussian boolean nextNextGaussian is valid
   */
  private static final ObjectStreamField[] serialPersistentFields = {
      new ObjectStreamField("seed", Long.TYPE),
      new ObjectStreamField("nextNextGaussian", Double.TYPE),
      new ObjectStreamField("haveNextNextGaussian", Boolean.TYPE)
  };

  /**
   * Reconstitute the {@code Random} instance from a stream (that is,
   * deserialize it).
   */
  private void readObject(java.io.ObjectInputStream s)
      throws java.io.IOException, ClassNotFoundException {

    ObjectInputStream.GetField fields = s.readFields();

    // The seed is read in as {@code long} for
    // historical reasons, but it is converted to an AtomicLong.
    long seedVal = fields.get("seed", -1L);
    if (seedVal < 0) {
      throw new java.io.StreamCorruptedException(
          "Random: invalid seed");
    }
    resetSeed(seedVal);
    nextNextGaussian = fields.get("nextNextGaussian", 0.0);
    haveNextNextGaussian = fields.get("haveNextNextGaussian", false);
  }

  /**
   * Save the {@code Random} instance to a stream.
   */
  synchronized private void writeObject(ObjectOutputStream s)
      throws IOException {

    // set the values of the Serializable fields
    ObjectOutputStream.PutField fields = s.putFields();

    // The seed is serialized as a long for historical reasons.
    fields.put("seed", seed.get());
    fields.put("nextNextGaussian", nextNextGaussian);
    fields.put("haveNextNextGaussian", haveNextNextGaussian);

    // save them
    s.writeFields();
  }

  // Support for resetting seed while deserializing
  private static final Unsafe unsafe = Unsafe.getUnsafe();
  private static final long seedOffset;

  static {
    try {
      seedOffset = unsafe.objectFieldOffset
          (Random.class.getDeclaredField("seed"));
    } catch (Exception ex) {
      throw new Error(ex);
    }
  }

  private void resetSeed(long seedVal) {
    unsafe.putObjectVolatile(this, seedOffset, new AtomicLong(seedVal));
  }
}
